Winnipeg tree experts say the extent of browning -- the desiccation of evergreen leaves -- appears to be unprecedented in recent memory.

'This is one of the worst years I've ever seen, if not the worst for browning'

-- City of Winnipeg forester Martha Barwinsky

Cedars, especially cultivars foreign to Manitoba, tend to be in the worst shape. But even some native white spruces have browned to the point they may not survive the summer.

"This is one of the worst years I've ever seen, if not the worst for browning," said City of Winnipeg forester Martha Barwinsky, who is responsible for the urban forest.

"Some winter browning is normal at this time of year. We tend to see it in some of the cedar cultivars that are not very hardy for this region. But this year in particular, I've noticed it's very bad."

Browning typically affects evergreens in the early spring, when the air warms well before the ground thaws. On sunny days, evergreen leaves can transpire, or give off moisture, while the ground surrounding the tree roots remain frozen.

As a result, coniferous trees effectively die of thirst.

Watering conifers before the winter freeze-up can help prevent spring browning. But the extreme cold Winnipeg experienced this past winter led the ground to freeze to a depth of two metres or more, extending the time it takes for the earth to thaw.

"The plants just aren't able to replenish the moisture loss from their leaves," Barwinsky said. Only recently have trees in Winnipeg started drawing water from their roots, she added. "Everything is about two weeks behind."

Cedars only make up a small percentage of the trees on city property. Non-native cedar cultivars are more commonly found on residential properties.

Right now, there's little a homeowner can do to help a tree that is suffering from browning.

"At this point, the damage has been done. People can possibly prune off the dead branches because they're not going to come back," said Carla Antonation, an arborist at Trilogy Tree Service. "It's just due to the dry summer we had and a winter that was especially cold and windy."

Barwinsky recommended waiting until mid-June to prune off dead branches or remove trees outright, as there's still a chance for some new growth to sprout in the coming weeks.

She said she would not even bother pruning. "I just leave it and let the tree figure it out," she said.

Anyone planting a new coniferous tree is advised to do it early in the spring and water extensively all summer and fall to ensure it gets established.

Arborists also recommend native species or locally developed cultivars -- with the caveat even they can succumb to unusually harsh weather.

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